-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 23/01/12 18:40, John Caron wrote: > On 1/23/2012 10:00 AM, plieger wrote: >> Dear All, >> >> >> We are struggling with finding the correct CF projection parameters for this >> data. The data is in >> satellite view projection, with the current settings we see a slight shift >> in IDV at the borders of >> the disc (internally we use proj4_params, which is not a CF standard): >> >> char projection ; >> projection:proj4_params = "+proj=geos +lon_0=0.000000 +lat_0=0 >> +h=35807.414063 +a=6378.169 >> +b=6356.5838" ; >> projection:long_name = "Projection information" ; >> projection:grid_mapping_name = "vertical_perspective" ; >> projection:latitude_of_projection_origin = 0.000000f ; >> projection:longitude_of_projection_origin = 0.000000f ; >> projection:perspective_point_height = 35807416.000000f ; >> projection:height_above_earth = 35807.414062f ; >> projection:false_easting = 0.000000f ; >> projection:false_northing = 0.000000f ; >> projection:EPSG_code = "none" ; >> >> Has anyone a suggestion regarding this issue? When opening these files in >> IDV you should set the >> "Data Source Type" to "Image Files (GINI)", otherwise you will have to wait >> a bit. When you open the >> variables latitude and longitude you will see that there is a slight shift >> which increases near the >> borders. >> >> Please let me know what you think! >> >> Thanks, >> Maarten >> > > Hi Martin: > > The IDV/CDM code uses a special projection for MSG, because (I think) > the vertical_perspective is not the exact > right projection, as you see by the pixels being a bit off. > > The MSG projection looks like: > > char Projection; > :*grid_mapping_name* = "MSGnavigation"; > :*longitude_of_projection_origin* = 0.0; // double > :*latitude_of_projection_origin* = 0.0; // double > :*semi_major_axis* = 6356755.5; // double > :*semi_minor_axis* = 6378140.0; // double > :*height_from_earth_center* = 4.2163970098E7; // double > :*scale_x* = 35785.830098; // double > :*scale_y* = -35785.830098; // double > > > details are here: > > http://www.unidata.ucar.edu/software/netcdf-java/reference/StandardCoordinateTransforms.html#MSG > > The tricky part is to get the projection coordinate x,y values correct. > The scale_x and scale_y are instrument specific, although Im not sure if > there > is more than one instrument. > > I kind of made this projection up based on > > > http://www.eumetsat.int/idcplg?IdcService=GET_FILE&dDocName=PDF_CGMS_03&RevisionSelectionMethod=LatestReleased > > and code ported from > > > http://www.eumetsat.int/idcplg?IdcService=GET_FILE&dDocName=zip_tools_msg_nav_c&RevisionSelectionMethod=LatestReleased > > Id be happy for some experts to review what Ive done and suggest changes > if needed.
Hi all, For information, I pushed a proposal to add the "GEOS" projection to the CF conventions, so that MSG would be supported. And as opposed to what is written in the Conventions, "vertical_perspective" is NOT the MSG native projection. Best regards, Martin -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (GNU/Linux) Comment: Using GnuPG with Red Hat - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJPHnk9AAoJEBdvyODiyJI4X6gIANQAVRFdyaZIvRNpvwzS2tEp eVQIL5BMkhY9mWAzzHoHyviLFhcxXnb8t2jltsanJFPsVG5ndU7/z2vh/CTzEflx 7b0xC/bYou5cUhNV6jc4N9lleGiHyFxUwHG0EfLQAr6Bi6cqYOYCz26+ux8iZVUt RnBpHK8baLbunzaZMfBiQzzS1cmrvV5LI6Eb9Yv5yb7sdmbwFigr2v4Im64xcySF y+N3LBP5mR4vWNOaHImvxzhgvehrzr2z2NKcii8p6iOS6V14SLCiGHxBx3KcdzgM 70K+B6K8prLnkTe+x5P+v3T3+c9iYlxc+0434bM4cX+lr4FFc/6Rupd+9vZGQIc= =dM1O -----END PGP SIGNATURE-----
<<attachment: martin_raspaud.vcf>>
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